Subject: [PATCH AUTOSEL 4.19 529/671] xsk: avoid store-tearing when assigning queues

From: Sasha Levin <[email-masked]>
Date: Thu, 16 Jan 2020 12:02:47 -0500

From: Björn Töpel <[email-masked]>

[ Upstream commit 94a997637c5b562fa0ca44fca1d2cd02ec08236f ]

Use WRITE_ONCE when doing the store of tx, rx, fq, and cq, to avoid
potential store-tearing. These members are read outside of the control
mutex in the mmap implementation.

Acked-by: Jonathan Lemon <[email-masked]>
Fixes: 37b076933a8e ("xsk: add missing write- and data-dependency barrier")
Signed-off-by: Björn Töpel <[email-masked]>
Signed-off-by: Daniel Borkmann <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 net/xdp/xsk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index c90854bc3048..b580078f04d1 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -320,7 +320,7 @@ static int xsk_init_queue(u32 entries, struct xsk_queue **queue,
 
 	/* Make sure queue is ready before it can be seen by others */
 	smp_wmb();
-	*queue = q;
+	WRITE_ONCE(*queue, q);
 	return 0;
 }
 
-- 
2.20.1